In many electronic systems, multiple voltage supply domains are used. In general, digital electronic signals on an integrated circuit are transported using the lowest possible voltage, given the fabrication technology of the circuit. However, representations of the same signals are sometimes necessary in voltage domains of a higher supply voltage. For example, higher voltages are used in analog or mixed-signal circuits, or circuits interfacing signals to external circuits.
Therefore, a crossing between the low-voltage domain and the high-voltage may be necessary. The actual signal crossing the domain boundaries may be represented in the low-voltage domain or in the high-voltage domain depending on the direction of converting. For example, some products may use a level shifter at some point in the design to convert low-voltage (e.g. from 1.0V supply) digital signals to high-voltage signals (e.g. from 1.8V supply).
The current level-shifters, however, are typically slow. In many circuits, the inherent low speed capabilities of this circuit are a problem. Further, when a long sequence of 0 or 1 is applied, an output of the current invertor may be high or low depending on its offset at the input and will simply amplify noise. When signal starts toggle again, the output signal during that time may have excessive duty cycle distortion or glitches. This disclosure discloses new methods and devices that solve these problems.